Water-based varnish using six points

1. Consider the smoothness and thickness of the paper

Paper quality has a certain impact on the quality of the glazing. When the paper with high smoothness is used, the glazing effect is better. On the contrary, if the surface of the paper is rough, the adsorption of the aqueous glazing oil is strong, and the glazing effect is easy to be caused, and the coating amount at the time of glazing is increased. .

In addition, paper thickness is also a factor to consider. Water-based glazing oil uses water as a solvent, which affects the water content of the paper during glazing and drying, which affects the stability of the paper size and ultimately affects the quality of the printed product. Generally thin paper is more affected.

2. Choose the right printing ink

The printing ink used for printing after printing must have solvent resistance and heat resistance. Otherwise, the printed image will be discolored or wrinkled or infested. The solution is to pay attention to the following points when selecting ink: use alcohol-resistant, ester-based solvent, acid-base ink; use ink that is not easy to change color and gloss; choose ink that has good adhesion to paper.

3. Control the viscosity of waterborne varnish

The viscosity of the waterborne varnish should be selected according to the specific conditions of the paper. If the viscosity of the aqueous varnish is too low, when the high-absorbent paper is coated, the paper will absorb the moisture in the aqueous varnish, which will cause the viscosity of the aqueous varnish to change too much, causing the surface of the printed product. Uneven coating, which affects the drying speed of the varnish film layer and the smoothness and gloss of the film layer after film formation. When the paper with poor absorption is coated, sag occurs, resulting in uneven film layer and poor drying. And other issues. If the viscosity of the aqueous varnish is too high, the fluidity is poor and it is not easy to level during coating. Therefore, the viscosity of the aqueous glazing oil for off-line glazing is recommended to be controlled for 18 to 24 seconds (4 cups, 25 ° C). The viscosity of the water-based glazing oil for on-line glazing is recommended to be controlled in 40 to 70 seconds (4 cups, 25 ° C).

The diluent used in the aqueous glazing oil is generally a 1:1 aqueous solution of alcohol. When the proportion of alcohol in the diluent is higher, the drying speed is faster, so it can be appropriately adjusted according to the specific conditions. It should be noted that it should not be excessively diluted, otherwise the abrasion resistance and gloss of the film layer will be lowered.

4. Use the correct amount of coating

By uniformly coating with the correct coating amount, a film layer having high gloss and high abrasion resistance can be formed. If the coating amount is too low, the aqueous coating oil may not form a continuous film layer, thereby lowering the gloss of the film layer; if the coating amount is too large, the film layer may be thickened, on the one hand, the production cost is increased, and the production cost is increased. On the one hand, it also affects the drying speed.

The control of the coating amount is related to factors such as the adsorption of the substrate to the varnish used and the use of glazing. Before using water-based varnish, the adsorption performance of the substrate on the aqueous varnish should be confirmed. At the same time, the use of glazing is also an important factor. Generally, in order to prevent the scratch of the printed product and enhance the gloss of the printed product, In the glazing treatment of wet-stacked wet (or wet-stacked), the coating amount of the aqueous glazing oil is 2 to 8 g/m 2 , and the coating amount is 2 to 4 g/m 2 when the glazing is performed before UV glazing. In the calender finishing, the coating amount is 10 to 20 g/m 2 .

5. Adjust the drying speed

In the process of using water-based glazing oil, if the drying speed is too slow, the film layer will not be completely dried, and even the back side scratches and sticks; if the drying speed is too fast, the paper will have excessive water loss and become brittle. A paper break has occurred, causing subsequent processing to malfunction. The drying speed of the water-based varnish can be adjusted by adjusting the drying temperature, the drying time, the content of the aqueous glazing diluent, and the ratio to achieve the desired drying effect.

6. Guarantee appropriate storage conditions

Water-based glazing oil can be sealed and stored at room temperature without shielding from light. The most suitable storage temperature is 20 ~ 25 ° C, the storage period can be up to six months. In particular, it is necessary to avoid freezing the temperature (below 0 ° C) to freeze it. Otherwise, even if it is completely melted after freezing, it will not return to a good state, and the gloss and abrasion resistance after film formation will decrease.